Refrigeration circuit

ABSTRACT

A refrigeration circuit ( 1   a ) comprises in the direction of flow of a circulating refrigerant a compressor unit ( 2 ) for compressing the refrigerant, a condenser ( 4 ), and at least one evaporator ( 10 ) having an expansion device ( 6 ) connected upstream thereof. The refrigeration circuit ( 1   a ) further comprises a subcooling temperature sensor ( 6 ) located at an outlet of the condenser ( 4 ) for measuring the temperature of refrigerant leaving the condenser ( 4 ), a control unit ( 12 ) functionally connected to the subcooling temperature sensor ( 6 ) and configured for detecting a leak in the refrigeration circuit ( 1   a ) based on the refrigerant temperature measured by the subcooling temperature sensor ( 6 ). The condenser ( 4 ) comprises a liquefying portion ( 4   a ) configured for at least partially liquefying the refrigerant and a subsequent subcooling portion ( 4   b ) configured for subcooling and storing liquefied refrigerant, and the outlet of the condenser ( 4 ), particularly the outlet of the subcooling portion ( 4   b ), is connected to the expansion device ( 8 ) of the at least one evaporator ( 10 ) through a receiver-free connection line ( 7 ).

The invention relates to a refrigeration circuit, and in particular arefrigeration circuit comprising means for leak detection.

Refrigeration circuits comprising in the direction of flow of acirculating refrigerant a compressor unit for compressing therefrigerant, at least one condenser and at least one evaporator having aexpansion device connected upstream thereof are well known in the art.

For allowing efficient operation of the refrigeration circuit an optimumrefrigerant charge is needed. This optimum charge varies with ambientconditions as e.g. the ambient temperature, and the cooling capacity,e.g. the number of cooling cabinets/coldrooms, to be supplied. To securethe respective optimum charge under all possible ambient conditions,typically a refrigerant receiver (or buffer) is provided. Saidrefrigerant receiver stores excessive liquid refrigerant which iscurrently not needed for optimum operation of the system, and releasesliquid refrigerant back to the system if more refrigerant is needed orif the system has lost refrigerant due to a leak. Said receivertypically is equipped with a device, e.g. a liquid level sensor, fordetecting the level of liquid stored within the receiver. In case ofrefrigerant being lost due to leakage, the liquid level sensor providesan alarm signal as soon as the level of refrigerant stored within thereceiver falls below the predetermined minimum liquid level. However,since the system usually comprises an amount of refrigerant which isconsiderably larger than the amount of refrigerant which is needed undermost operation conditions, the system may lose a large amount ofrefrigerant before the predetermined minimum refrigerant level isreached and the alarm is set off.

It therefore would be beneficial to provide a refrigeration circuitcomprising improved leak detection means allowing to detect even smallleaks of the refrigeration circuit at an early stage of the leakage.

It further would be beneficial to provide a refrigeration circuit whichmay be produced and operated at low costs and which does occupy onlylittle space.

A refrigeration circuit according to exemplary embodiments of theinvention comprises in the direction of flow of a circulatingrefrigerant: a compressor unit for compressing the refrigerant; acondenser; and at least one evaporator having an expansion deviceconnected upstream thereof; the refrigeration circuit further comprisinga subcooling temperature sensor located at an outlet of the condenserfor measuring the temperature of refrigerant leaving the condenser; acontrol unit functionally connected to the subcooling temperature sensorand configured for detecting a leak in the refrigeration circuit basedon the refrigerant temperature measured by the subcooling temperaturesensor, wherein the condenser comprises a liquefying portion configuredfor at least partially liquefying the refrigerant and a subsequentsubcooling portion configured for subcooling and storing liquefiedrefrigerant; wherein the outlet of the condenser, particularly theoutlet of the subcooling portion, is connected to the expansion deviceof the at least one evaporator through a receiver-free connection line.The subcooling portion is connected either directly to the liquefyingportion, i.e. without an additional device arranged between theliquefying portion and the subcooling portion, or only by means of agas-liquid-separator as it will be described in detail with reference toFIG. 3.

A method for detecting a leak in a refrigeration circuit according tofurther exemplary embodiments of the invention comprises the steps ofcompressing the refrigerant; at least partially liquefying therefrigerant in a liquefying portion of a condenser; flowing the at leastpartially liquefied refrigerant from the liquefying portion to asubsequent subcooling portion of the condenser; subcooling therefrigerant in the subcooling portion of the condenser; leading therefrigerant from the outlet of the condenser, particularly the outlet ofthe subcooling portion, to an expansion device of at least oneevaporator in a direct, receiver-free manner, and evaporating therefrigerant; the method further comprising the steps of measuring thetemperature of the liquid refrigerant leaving the subcooling portion ofthe condenser; and detecting a leak in the refrigeration circuit basedon the liquid temperature measured by the subcooling temperature sensor.The at least partially liquefied refrigerant is lead to the liquefyingportion either directly, i.e. without an additional device arrangedbetween the liquefying portion and the subcooling portion, or by meansof a gas-liquid-separator separating the gaseous portion from the liquidportion as it will be described in detail with reference to FIG. 3.

Exemplary embodiments of the invention are described in detail belowwith reference to the figures, wherein:

FIG. 1 shows a schematic view of a refrigeration circuit according to afirst exemplary embodiment of the invention.

FIG. 2 shows a schematic view of a refrigeration circuit according to asecond exemplary embodiment of the invention.

FIG. 3 shows a schematic view of a refrigeration circuit according to athird exemplary embodiment of the invention.

FIG. 1 shows a schematic view of a refrigeration circuit 1 a accordingto a first exemplary embodiment of the invention.

The refrigeration circuit 1 a comprises in the direction of flow of acirculating refrigerant, which is indicated by arrow A, a compressorunit comprising at least one compressor 2 for compressing therefrigerant; at least one condenser 4 and at least one evaporator 10having a corresponding expansion device 8 connected upstream thereof.

The at least one condenser 4 comprises an upstream-side liquefyingportion 4 a fluidly connected to an outlet of the compressor 2 andconfigured for at least partially liquefying the refrigerant supplied bythe compressor 2, and a subsequent downstream-side subcooling portion 4b, which is configured for subcooling and storing the refrigerant, whichhas been liquefied by the liquefying portion 4 a of the condenser 4. Anoutlet of the liquefying portion 4 a is connected directly to theliquefying portion 4 b, i.e. the liquefying portion 4 a and thesubcooling portion 4 b are either formed integrally with each otherand/or are connected by means of a receiver-free connection line, sothat the refrigerant, which has been liquefied within the liquefyingportion 4 a flows directly from the liquefying portion 4 a into thesubcooling portion 4 b. The outlet of the condenser 4, in particular theoutlet of the subcooling portion 4 b, is fluidly connected to theexpansion device 8 of the at least one evaporator 10 by means of areceiver-free connection line 7, so that the liquefied and subcooledrefrigerant flows directly, i.e. without passing a receiver, from thesubcooling portion 4 b into the expansion device 8 without passinganother device, in particular without passing a receiver.

The subcooling portion 4 b of the condenser 4 is not only configured forsubcooling the liquefied refrigerant, but also for storing any excessiveliquid refrigerant, which is not needed for the operation of therefrigeration circuit 1 a under the current ambient conditions in orderto fulfill the actual cooling demands. As a result, contrary to theprior art, there is no need to provide an additional receiver forstoring the excessive refrigerant.

A subcooling temperature sensor 6 is provided a the outlet of thesubcooling portion 4 b of the condenser 4 in order to measure thetemperature of the liquefied and subcooled refrigerant leaving thecondenser 4.

An expansion device 8 for expanding the liquefied and subcooledrefrigerant is provided downstream of the subcooling temperature sensor6. The expanded refrigerant leaving the expansion device 8 is deliveredto at least one evaporator 10 fluidly connected between an outlet of theexpansion device 8 and an inlet of the at least one compressor 2. Insaid at least one evaporator 10 the refrigerant is evaporated therebyproviding the desired cooling capacity of the refrigeration circuit 1 a.

In the exemplary embodiment shown in FIG. 1, only a single compressor 2,a single condenser 4, a single expansion device 8 and a singleevaporator 10 are respectively shown; the skilled person, however, willeasily understand that a plurality of each of said devices 2, 4, 8, 10may be provided if necessary or desired. E.g. a plurality of evaporators10 respectively comprising an associated expansion device 8 may beprovided in order to provide a plurality of heat sinks, which are e.g.installed in a number of refrigerated goods presentation furnituresprovided in a supermarket.

The subcooling temperature sensor 6 is functionally, e.g. electrically,connected to a control unit 12, which is configured for operating asleakage detection system by monitoring the temperature signal providedby the subcooling temperature sensor 6. In particular, the control unit12 may be configured to compare the actual temperature signal providedby the subcooling temperature sensor 6 with a predetermined temperature,which is calculated and/or stored by means of a calculation and/orstorage unit 14 provided within the control unit 12.

If the control unit 12 detects a leakage of refrigerant from therefrigeration circuit 1 a, it sets off an alarm, e.g. an optical and/oran acoustical alarm, by means of at least one appropriate alarm device16, 18 functionally connected to the control unit 12. Additionally oralternatively, the control unit 12 may stop the operation of thecompressor(s) 2, in order to avoid a further loss of refrigerant.Alternatively, the compressor(s) 2 may be operated at reduced speed inorder to provide at least partial refrigeration capacity without loosingto much refrigerant.

The calculation and/or storage unit 14 may calculate the predeterminedtemperature or select the predetermined temperature to be compared withthe measured temperature from a plurality of stored values based ontemperatures measured by at least on additional temperature sensor 20,22, 24, 26 including e.g. an ambient air temperature sensor 20 and/orrefrigerant temperature sensors 22, 24, 26 which are provided at furtherpositions of the refrigeration circuit 1 a for measuring the temperatureof the refrigerant circulating within the refrigeration circuit 1 a.

The calculation and/or selection of the predetermined temperature mayalso be based on an external value, e.g. a desired cooling capacity,which has been input by an operator by means of an input device 28connected to the control unit 12.

Example calculations for a refrigeration circuit, in which theevaporating temperature, the superheating at the evaporator 10 and thecooling capacity have been kept constant, have been carried out:

Evaporating Temperature −10° C. Superheat Evaporator 10 K CoolingCapacity 100 kW

In a first step, the influence of ambient temperature on the subcoolingwith constant refrigerant charge has been examined:

1. Initial charge:

Input: Refrigerant Charge 23.4 kg Ambient temperature T_(amb) 35° C.Output: Subcooling temperature T_(sub) 3 K

2. Change of Ambient Temperature:

Input: Refrigerant Charge 23.4 kg Ambient temperature T_(amb) 25° C.Output: Subcooling temperature T_(sub) 4.7 K

I.e. a decrease of the ambient temperature T_(amb) of ΔT_(amb)=−10° C.results in an increase of the subcooling temperature T_(sub) measured bythe temperature sensor 6 of ΔT_(sub)=+1.7 K (from 3 K to 4.7 K).

In a second step, the influence of charge loss on the subcoolingtemperature at constant ambient temperature as been evaluated:

1. Initial charge

Input: Ambient temperature T_(amb) 25° C. Refrigerant Charge 23.4 kgOutput: Subcooling T_(sub) 4.7 K

2. Loss of charge of 5% (=1.17 kg)

Input: Ambient temperature T_(amb) 25° C. Refrigerant Charge 22.21 kgOutput: Subcooling T_(sub) 3.6 K

Thus, there occurs a difference of ΔT_(sub)=1.1 K between the expectedsubcooling temperature of 4.7 K and the actually measured subcoolingtemperature of 3.6 K, which indicates that there is a loss ofrefrigerant in the system.

Performing a number of test calculations may even allow to determine theamount of refrigerant lost by comparing the expected (calculated) andthe actually measured subcooling temperatures T_(sub).

FIG. 2 shows a schematic view of a refrigeration circuit 1 b accordingto a second exemplary embodiment of the invention.

The refrigeration circuit 1 b according to the second embodimentcomprises basically the same components as the refrigeration circuit 1 aof the first embodiment, namely in the direction of flow of acirculating refrigerant, as indicated by arrow A, a compressor unitcomprising at least one compressor 2 for compressing the refrigerant; acondenser 4 and at least one evaporator 10 a, 10 b having acorresponding expansion device 8 a, 8 b connected upstream thereof. Thecomponents of the refrigeration circuit 1 b according to the secondembodiment, which are identical to the corresponding components of therefrigeration circuit 1 a according to the first embodiment shown inFIG. 1 are denoted by the same reference signs and will not be discussedin detail again.

The refrigeration circuit 1 b according to a second exemplary embodimentof the invention comprises two or more evaporators 10 a, 10 b having arespective expansion device 8 a, 8 b connected upstream of each of theevaporators 10 a, 10 b, wherein the outlet of the condenser 4, inparticular the outlet of the subcooling portion 4 b, is connected to therespective expansion devices 8 a, 8 b of the two or more evaporators 10a, 10 b by a receiver-free connection line 7 branching intoreceiver-free branch lines 9 a, 9 b connecting with the respectiveexpansion devices 8 a, 8 b.

Refrigerant temperature sensors 22, 23 may be arranged at each of theconduits connecting the expansion devices 8 a, 8 b to the respectivelyassociated evaporator 10 a, 10 b.

Each of the expansion devices 8 a, 8 b may be provided as a switchableexpansion device 8 a, 8 b, which is switchable between an open state, inwhich it expands the refrigerant circulating within the refrigerationcircuit 1 b, and a closed state, in which it blocks the flow ofrefrigerant through the associated evaporator 10 a, 10 b allowing toselectively activate and deactivate the operation of each of theevaporators 10 a, 10 b.

As a further option the degree of expansion provided by the expansiondevices 8 a, 8 b may be adjustable.

It is also possible to use a single, common expansion device 8 fordelivering expanded refrigerant to two or more evaporators 10 a, 10 b.

FIG. 3 shows a schematic view of a refrigeration circuit 1 c accordingto a third exemplary embodiment of the invention.

The refrigeration circuit 1 c according to the third embodimentcomprises basically the same components as the refrigeration circuit 1 aof the first embodiment, namely in the direction of flow of acirculating refrigerant, as indicated by arrow A, a compressor unitcomprising a compressor 2 for compressing the refrigerant; a condenser40 and an evaporator 10 having a corresponding expansion device 8connected upstream thereof. The components of the refrigeration circuit1 c according to the third embodiment, which are identical to thecorresponding components of the refrigeration circuit 1 a according tothe first embodiment shown in FIG. 1 are denoted by the same referencesigns and will not be discussed in detail again.

The condenser 40 according to the third embodiment differs from thecondenser 4 of the first embodiment in that a gas-liquid separator 42 isprovided between the liquefying portion 40 a and the subsequentsubcooling portion 40 b of the condenser 40.

The gas-liquid separator 42 is configured for separating a gas portionfrom a liquid portion of a gas-liquid-mixture, which leaves theliquefying portion 40 a of the condenser 40 in case the condensingcapacity of the liquefying portion 40 a is not sufficient for condensingall gaseous refrigerant delivered from the compressor 2 to theliquefying portion 40 a of the condenser 40. In the third embodiment theliquid portion of the gas-liquid-mixture is delivered to the subcoolingportion 40 b of the condenser 40 for subcooling and storage, as in thefirst embodiment shown in FIG. 1, and the separated gas portion of thegas-liquid-mixture is delivered by means of a gas-return-line 44 back tothe entry of the liquefying portion 40 a in order to pass the liquefyingportion 40 a again for being liquefied as well.

As a result, in a refrigeration circuit 1 c according to the thirdembodiment only liquefied refrigerant is delivered to the subcoolingportion 40 b of the condenser 40 which increases the efficiency of thesubcooling portion 40 b. This enhances the efficiency of therefrigeration circuit 1 c, as in a refrigeration circuit 1 b accordingto the third embodiment no gaseous refrigerant exits the condenser 40and enters into the at least one expansion device 8.

A refrigeration circuit according to an exemplary embodiment of theinvention comprises in the direction of flow of a circulatingrefrigerant a compressor unit for compressing the refrigerant, at leastone condenser, and at least one evaporator having an expansion deviceconnected upstream thereof. The condenser comprises a liquefying portionconfigured for at least partially liquefying the refrigerant and asubsequent subcooling portion, which is configured for subcooling andstoring the liquefied refrigerant. The outlet of the liquefying portionis connected to the subcooling portion by means of a receiver-freeconnection line, so that the liquefied refrigerant flows directly, i.e.without passing a receiver, from the liquefying portion into thesubcooling portion. The outlet of the condenser, in particular theoutlet of the subcooling portion, is connected to the expansion deviceof the at least one evaporator by means of a direct, in particularreceiver-free, connection line so that the liquefied and subcooledrefrigerant exiting the condenser flows from the subcooling portion intothe expansion device without passing another device, in particularwithout passing a receiver.

A method for detecting a leak in a refrigeration circuit according to anexemplary embodiment of the invention comprises the steps of compressingthe refrigerant; at least partially liquefying the refrigerant in aliquefying portion of a condenser; leading the at least partiallyliquefied refrigerant from the liquefying portion to an immediatelysubsequent subcooling portion of the condenser; subcooling therefrigerant in the subcooling portion of the condenser; leading therefrigerant from the outlet of the condenser, particularly the outlet ofthe subcooling portion, to an expansion device of at least oneevaporator in a direct, i.e. receiver-free, manner, and evaporating therefrigerant. The method further comprises the steps of measuring thetemperature of the liquid refrigerant leaving the subcooling portion ofthe condenser and detecting a leak in the refrigeration circuit based onthe liquid temperature measured by the subcooling temperature sensor.

The refrigeration circuit according to an exemplary embodiment of theinvention further comprises a subcooling temperature sensor, which islocated at an outlet of the condenser and which is configured formeasuring the temperature of refrigerant leaving the subcooling portionof the condenser, and a control unit, which is functionally connected tothe temperature sensor and configured for detecting a leak in therefrigeration circuit based on the refrigerant temperature measured bythe temperature sensor.

According to an exemplary embodiment of the invention, measuring andmonitoring the temperature of the liquefied refrigerant leaving thecondenser and in particular leaving the subcooling portion of thecondenser allows to detect even a small loss of refrigerant from therefrigeration circuit with high reliability and accuracy. Thus anyleakage of refrigerant may be reliably detected at an early stage ofleakage even if a large amount of refrigerant is still present in thecircuit, and the loss of a large amount of refrigerant can be avoided.

As the refrigeration circuit according to exemplary embodiments of theinvention does not comprise a receiver, the costs and the space forproviding such a receiver are saved. Thus, the refrigeration circuit maybe produced and operated at low costs and occupies only little space.

In an embodiment the control unit comprises a comparison unit which isconfigured for comparing the temperatures measured by the subcoolingtemperature sensor to at least one predetermined value. Comparing thetemperatures measured by the subcooling temperature sensor to at leastone predetermined value allows an easy and reliable leak detection, asin case a leakage occurs, the subcooling temperature will considerablychange and deviate from the predetermined value(s).

In an embodiment the control unit comprises a calculation unit which isconfigured for calculating the predetermined value(s). Providing such acalculation unit allows to calculate the predetermined value(s) based onthe actual ambient and operating conditions of the refrigerationcircuit. It therefore allows to flexibly adjust the predetermined valueto said ambient and operating conditions.

In an embodiment the control unit further comprises a storing unit,which is configured for storing at least one predetermined value, whichhas been calculated before and/or which has been entered from anexternal source into the storing unit. Using stored values aspredetermined values allows to save the cost for providing thecalculation unit and/or to use predetermined values calculated by meansof simulations, which have been carried out on elaborated computer basedexternal simulation system. Alternatively or additionally, predeterminedvalues, which have been measured before, in particular during theoperation of the actual system, may be stored and used.

In an embodiment the refrigeration circuit comprises at least oneadditional temperature sensor, which is functionally connected to thecontrol unit, and the control unit is configured for calculating thepredetermined value and/or selecting the predetermined value from aplurality of stored predetermined values by using the temperature valuemeasured by the at least one of the additional temperature sensors. Theat least one additional temperature sensors may be one of an ambient airtemperature sensor or a temperature sensor which is configured formeasuring the temperature of the circulating refrigerant at a differentposition of the refrigeration circuit. This allows to adjust thepredetermined value to the actual ambient temperature and/or to thetemperature(s) of the refrigerant circulating within the refrigerationcircuit.

In an embodiment the control unit is configured to stop the operation ofthe at least one compressor and/or to set off an alarm signal afterdetecting a leakage of the refrigeration circuit in order to avoid afurther loss of refrigerant.

In an embodiment a gas-liquid-separator is arranged between theliquefying portion and the subcooling portion of the condenser, an inletof the gas-liquid-separator being fluidly connected to an outlet of theliquefying portion of the condenser, a gas outlet of thegas-liquid-separator being fluidly connected to an inlet of theliquefying portion of the condenser, and a liquid outlet of thegas-liquid-separator being fluidly connected to an inlet of thesubcooling portion of the condenser for delivering the gas-phase to theinlet of the liquefying portion to be liquefied. Such agas-liquid-separator allows to separate a gas portion and a liquidportion from a gas-liquid-mixture leaving the liquefying portion of thecondenser. Delivering only liquid refrigerant to the subcooling portionenhances its efficiency and the efficiency of refrigeration circuit.

In an embodiment two or more evaporators having a respective expansiondevice connected upstream thereof are provided. In said embodiment theoutlet of the condenser, particularly the outlet of the subcoolingportion, is connected to the respective expansion devices of the two ormore evaporators by a receiver-free connection line branching intoreceiver-free branch lines connecting to the respective expansiondevices. Providing a plurality of evaporators allow to provide aplurality of heat sinks at different locations, e.g. in a number ofrefrigerated goods presentation furnitures provided in a supermarket,which are operated by a single refrigeration circuit.

While the invention has been described with reference to an exemplaryembodiment, it will be understood by those skilled in the art thatvarious changes may be made and equivalents may be substituted forelements thereof without departing from the scope of the invention. Inaddition, modifications may be made to adapt a particular situation ormaterial to the teachings of the invention without departing from theessential scope thereof. Therefore, it is intended that the invention isnot limited to the particular embodiment disclosed, but that theinvention will include all embodiments falling within the scope of theappended claims.

-   1 a, 1 b, 1 c refrigeration circuit-   2 compressor unit-   4, 40 condenser-   4 a, 40 a liquefying portion-   4 b, 40 b subcooling portion-   6 subcooling temperature sensor-   7 receiver-free connection line-   8, 8 a, 8 b expansion device-   9 a, 9 b branch lines-   10, 10 a, 10 b evaporator-   12 control unit-   14 calculation and/or storage unit-   16 acoustical alarm means-   18 optical alarm means-   20 ambient air temperature sensor-   22, 23, 24, 26 refrigerant temperature sensors-   28 input device-   42 gas-liquid-separator-   44 gas-return-line

1. A refrigeration circuit comprising in the direction of flow of acirculating refrigerant: a compressor unit for compressing therefrigerant; a condenser; and at least one evaporator having anexpansion device connected upstream thereof; the refrigeration circuitfurther comprising: a subcooling temperature sensor located at an outletof the condenser for measuring the temperature of refrigerant leavingthe condenser; a control unit functionally connected to the subcoolingtemperature sensor and configured for detecting a leak in therefrigeration circuit based on the refrigerant temperature measured bythe subcooling temperature sensor compared to a predeterminedtemperature calculated based on (i) at least one temperature measuredoutside the condenser or (ii) an external value input by an operator;wherein the condenser comprises a liquefying portion configured for atleast partially liquefying the refrigerant and a subsequent subcoolingportion configured for subcooling and storing liquefied refrigerant; andwherein the outlet of the condenser, particularly the outlet of thesubcooling portion, is connected to the expansion device of the at leastone evaporator through a receiver-free connection line.
 2. Therefrigeration circuit of claim 1, wherein, the subcooling portion isconnected to the liquefying portion without a further device arranged inbetween, or only by means of a gas-liquid-separator.
 3. Therefrigeration circuit of claim 1, wherein the control unit comprises acomparison unit which is configured for comparing the temperaturemeasured by the subcooling temperature sensor to a predetermined value.4. The refrigeration circuit of claim 3, wherein the control unitfurther comprises a calculation unit which is configured for calculatingthe predetermined value.
 5. The refrigeration circuit of claim 3,wherein the control unit further comprises a storing unit which isconfigured for storing at least one predetermined value.
 6. Therefrigeration circuit of claim 4, further comprising at least oneadditional temperature sensor functionally connected to the controlunit, wherein the control unit is configured for calculating and/orselecting the predetermined value using the temperature value measuredby the at least one of the additional temperature sensors.
 7. Therefrigeration circuit of claim 6, wherein the at least one additionaltemperature sensor is at least one of an ambient air temperature sensorand a temperature sensor configured for measuring the temperature of therefrigerant circulating within the refrigeration circuit.
 8. Therefrigeration circuit of claim 4, wherein the control unit is configuredto reduce or even stop the operation of the at least one compressorand/or to set off an alarm signal after detecting a leakage of therefrigeration circuit.
 9. The refrigeration circuit of claim 1, whereina gas-liquid-separator is arranged between the liquefying portion andthe subcooling portion of the condenser, an inlet of thegas-liquid-separator being fluidly connected to an outlet of theliquefying portion of the condenser.
 10. The refrigeration circuit ofclaim 9, wherein a gas outlet of the gas-liquid-separator is fluidlyconnected to an inlet of the condenser, and wherein a liquid outlet ofthe gas-liquid-separator is fluidly connected to an inlet of thesubcooling portion of the condenser.
 11. The refrigeration circuit ofclaim 1, wherein two or more evaporators having a respective expansiondevice connected upstream thereof are provided, and wherein the outletof the condenser, particularly the outlet of the subcooling portion, isconnected to the respective expansion devices of the two or moreevaporators by a receiver-free connection line branching intoreceiver-free branch lines connecting to the respective expansiondevices.
 12. A method for detecting a leak in a refrigeration circuitcomprising: compressing the refrigerant; at least partially liquefyingthe refrigerant in a liquefying portion of a condenser; flowing the atleast partially liquefied refrigerant from the liquefying portion to asubsequent subcooling portion of the condenser; subcooling therefrigerant in the subcooling portion of the condenser; leading therefrigerant from the outlet of the condenser, particularly the outlet ofthe subcooling portion, to an expansion device of at least oneevaporator in a receiver-free manner, and evaporating the refrigerant;the method further comprising: measuring the temperature of the liquidrefrigerant leaving the subcooling portion of the condenser; anddetecting a leak in the refrigeration circuit based on the liquidrefrigerant temperature measured by the subcooling temperature sensorcompared to a predetermined temperature calculated based on (i) at leastone temperature measured outside the condenser or (ii) an external valueinput by an operator.
 13. The method of claim 12, wherein the at leastpartially liquefied refrigerant is led from the liquefying portion tothe subcooling portion without passing a further device except for anoptional gas-liquid-separator.
 14. The method of claim 12, wherein therefrigerant is led from the outlet of the condenser, particularly theoutlet of the subcooling portion, to two or more evaporators having arespective expansion device connected upstream thereof, through adirect, receiver-free connection line branching into receiver-freebranch lines connecting to the respective expansion devices.
 15. Themethod of claim 12, further comprising separating the gas phase from theliquid phase of at least partially liquefied refrigerant, delivering theliquid phase to the subcooling portion of the condenser and deliveringthe gas phase to the liquefying portion of the condenser.